The spread is a fatal crop disease known as citrus greening.Â It is killing citrus trees by the thousands --primarily in southern Florida. Now growers are moving to North Central Florida where nurseries are working to prevent contamination.

Dr. Timothy Schubert, plant pathologist at the University of Florida says the signs of citrus greening are obvious, "The fruit eventually becomes small, off-flavored, they don't ripen normally, falloff the tree prematurely before even approaching ripeness."

The disease which is spread by insects has been detected as far west as Texas. University of Florida researchers are working on finding solutions.